When World War II traffic levels over-stressed the existing UP passenger-locomotive stud, the railroad returned to Alco for 10 more of the FEF design. They might have preferred to buy diesel sets, but those were not available. Instead, Alco produced engines with the power dimensions and driver diameters of the FEF-2 (Locobase 284) under a boiler virtually identical to that of the FEF-1 (Locobase 8339). And like the FEF-1, SKF supplied the leading and trailing truck roller bearings while Timken produced those for the driving axles.
Although delivered with 69.5 sq ft of arch tubes, these were removed in 1945.
The last of the class - 844 - never actually left service. Its 1957-1959 stint of freight work was its last revenue work, but it was reserved for excursion work in 1960. Renumbered for a time as 8444, the locomotive regained its original number in 1969 after the diesel that bore 844 was retired. It was reassigned to excursion work and ran into the 21st Century.
The other 9 were all retired in 1957-1962.
| Specifications | |
|---|---|
| Class | FEF-3 |
| Locobase ID | 8340 |
| Railroad | Union Pacific (UP) |
| Whyte | 4-8-4 |
| Road Numbers | 835-844 |
| Gauge | Std |
| Builder | Alco |
| Year | 1944 |
| Valve Gear | Walschaert |
| Locomotive Length and Weight | |
| Driver Wheelbase | 22' |
| Engine Wheelbase | 50.92' |
| Ratio of driving wheelbase to overall engine wheebase | 0.43 |
| Overall Wheelbase (engine & tender) | 98.42' |
| Axle Loading (Maximum Weight per Axle) | |
| Weight on Drivers | 266490 lbs |
| Engine Weight | 486340 lbs |
| Tender Light Weight | 421550 lbs |
| Total Engine and Tender Weight | 907890 lbs |
| Tender Water Capacity | 23500 gals |
| Tender Fuel Capacity (oil/coal) | 6000 gals |
| Minimum weight per yard of rail on which locomotive could run | 111.04 lb rail |
| Geometry Relating to Tractive Effort | |
| Driver Diameter | 80" |
| Boiler Pressure | 300 psi |
| Cylinders (dia x stroke) | 25" x 32" |
| Tractive Effort | 63750 lbs |
| Factor of Adhesion (Weight on Drivers/Tractive Effort) | 4.18 |
| Heating Ability | |
| Firebox Area | 442 sq. ft |
| Grate Area | 100.20 sq. ft |
| Evaporative Heating Surface | 4225 |
| Superheating Surface | 1400 |
| Combined Heating Surface | 5625 |
| Evaporative Heating Surface/Cylinder Volume | 232.39 |
| Computations Relating to Power Output (More Information) | |
| Robert LeMassena's Power Computation | 30060 |
| Same as above plus superheater percentage | 37541.60 |
| Same as above but substitute firebox area for grate area | 165602.67 |
| Power L1 | 41880.01 |
| Power MT | 1385.86 |
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